Although the Internet has had great successes in facilitating communications between computer systems and enabling electronic commerce, the computer systems connected to the Internet have been under almost constant attack by hackers seeking to disrupt their operation. Many of the attacks seek to exploit vulnerabilities of software systems including application programs or other computer programs executing on those computer systems. Developers of software systems and administrators of computer systems of an enterprise go to great effort and expense to identify and remove vulnerabilities. Because of the complexity of software systems, however, it is virtually impossible to identify and remove all vulnerabilities before software systems are released. After a software system is released, developers can become aware of vulnerabilities in various ways. A party with no malicious intent may identify a vulnerability and may secretly notify the developer so the vulnerability can be removed before a hacker identifies and exploits it. If a hacker identifies a vulnerability first, the developer may not learn of the vulnerability until it is exploited—sometimes with disastrous consequences.
Regardless of how a developer finds out about a vulnerability, the developer typically develops and distributes to system administrators “patches” or updates to the software system that remove the vulnerability. If the vulnerability has not yet been exploited (e.g., might not be known to hackers), then a developer can design, implement, test, and distribute a patch in a disciplined way. If the vulnerability has already been widely exposed, then the developer may rush to distribute a patch without the same care that is used under normal circumstances. When patches are distributed to the administrators of the computer systems, they are responsible for scheduling and installing the patches to remove the vulnerabilities.
Unfortunately, administrators often delay the installation of patches to remove vulnerabilities for various reasons. When a patch is installed, the software system and possibly the computer system on which it is executing may need to be shut down and restarted. If the vulnerability is in a software system that is critical to the success of an organization, then the administrator needs to analyze the tradeoffs of keeping the software system up and running with its associated risk of being attacked and of shutting down a critical resource of the enterprise to install the patch. Some administrators may delay the installation of the patch because they fear that, because of a hasty distribution, it might not be properly tested and have unintended side effects. If the patch has an unintended side effect, then the software system, the computer system, or some other software component that is impacted by the patch may be shut down by the patch itself. Administrators need to factor in the possibility of an unintended side effect when deciding whether to install a patch. These administrators may delay installing a patch until experience by others indicates that there are no serious unintended side effects.
Intrusion detection systems have been developed that can be used to identify whether an attempt is being made to exploit a known vulnerability that has not yet been patched. These intrusion detection systems can be used to prevent exploitations of newly discovered vulnerabilities for which patches have not yet been developed or installed. These intrusion detection systems may define a “signature” for each way a vulnerability can be exploited. For example, if a vulnerability can be exploited by sending a certain type of message with a certain attribute, then the signature for that exploitation would specify that type and attribute. When a security enforcement event occurs, such as the receipt of a message, the intrusion detection system checks its signatures to determine whether any match the security enforcement event. If so, the intrusion detection system may take action to prevent the exploitation, such as dropping the message.
Signatures for newly discovered exploitations of vulnerabilities can be created in different ways. Developers of intrusion detection systems may create and distribute new signatures when they become aware of new exploitations. An administrator can then install the new signatures to prevent the exploitation. A developer may not, however, provide signatures for all known exploitations. For example, the vulnerability may be in a special-purpose application program that the developer does not support. To prevent exploitation of such a vulnerability, intrusion detection systems may allow administrators to create their own signatures.
A set of one or more signatures may be considered a security policy. Developers of intrusion detection systems may provide various security policies. For example, a developer may provide one security policy that defines signatures of vulnerabilities of an operating system and many other security policies that are specific to an application or a class of applications. Similarly, an administrator may define a security policy that is specific to custom applications used by the enterprise.
Because intrusions can occur at various points within an operating system or an application, intrusion detection systems have been developed to detect and prevent exploitation of vulnerabilities at each of these points. For example, an intrusion detection system may be developed to prevent exploitation of vulnerabilities that can be detected at the network layer of a communication protocol, and another intrusion detection system may be developed to prevent exploitation of vulnerabilities that can be detected when a file is accessed. Each developer of an intrusion detection system can provide their own implementation and security policies that need to be distributed to each computer system to be protected. In addition, any updates to the implementation or security policies also need to be distributed to the computer systems to be protected.
The distribution and updating of security policies for an enterprise with a large number of computer systems can be a complex and time-consuming task. Each security policy needs to be provided to each computer system and then to the appropriate intrusion detection system that is installed on the computer system. Since the developers of intrusion detection systems typically develop their systems independent of each other, each intrusion detection system may have a proprietary mechanism for defining and distributing security policies. A system administrator of an enterprise may need to be aware of each of these mechanisms to use the intrusion detection system effectively.
It would be desirable to have a mechanism that would provide a uniform way to distribute security policies received at a computer system to components responsible for enforcing the security policies.